Manufacture of light-sensitive films



Patented Jul 8, 1930 UNITED STATES ULRICH DIEM-BERNET, 01 SPEIGHER,SWITZERLAND mannracrunn or uen'r-snnsrrrvn runs No'Drawing.Application-filed 1m} 17, 1927, Serial 1%. 192,168, and in Switzerlandand Germany It is known to produce a light sensitive film having nosensitive co ting from cellulosesodium-xanthate (viscose) and; havingthe. sensitiz'er within the film'material. Such 5 known film is preparedlike the sensitive salt papers by, treating finished films hithertomainly used as a transparent packing ma- 7 terial, in one or more bathsof water containing solutions of sensitiz'ers and impregnating 10 themthus with light sensitive materials. In each of these baths the filmswells and extends in every direction and subsequently contracts duringthe drying operation, whereby .the original dimensions are only reachedunder the most favorable circumstances. The divergence from the originalsize is the greater,

the larger the number of baths through which the film has to be passed.

This is a disadvantage which renders such films unsuitable for certalnphotographic pure poses and particularly for the cinematographic'art.

The present process has for its object to produce from viscose lightsensitive negative and dia-positive films which have no sensitivecoating but are sensitized within the body of the film and which aresubjected to much less variations in tension than the impregnated filmhaving no coating and produced by the hitherto known processes. In ,-.contradistinction to the known process-am. hich has been;

cording to which the film, manufactured (i. e., cast, coagulated, washedand dried) ready for sale without additions of sensitizers, isimpregnated with sensitizing materials 'later on, the novel process comsists in sensitizing the film mass already during the manufacture i'.e., at least before the ultimate and complete drying of the film, 40while the latter is still moist and therefore in its swollen condition.This is effected in that either all the sensitizing agents on at leastone of the components used for sensi-v tizing purposes is incorporatedin the film mass, for example after a purification bath with which thecast but not yet finished film is treated, preferably after the lastpurifi-.;

cation or washing bath. Preferably, simultaneously or in a subsequentstep of the process, by the addition of tanning substances,

a further reducton of the susceptibility towards water and eventually ofthe inflammability of the film mass may be obtained.

In producing such a light sensitive film from viscose and which has nosensitive coatmg the present process In be carried into effect byimbuing the film, or example after a purifying bath with for instance aferric salt solution (ammonium-ferric-citrate). The sensitizing of thefilm mass with a silver on halidmay be effected b v first adding to thefilm the halogen source for instance sodium-' chloride, ammoniumbromide), whereupon the film charged with this component is eitherdirectly or after superficial drying impreg- 65 nated with a silversolution for instance with silver nitrate in order to cause theformation of silver halid. A tanning of the film mass may be causedeither durin ijthe casting of the film ima bath containing or lnstancealum, or ammonium salts, or it is caused subsequently to the castvmg ofthe film by smoking the sensitized film,

for instance in formaldehyde vapours.

The light sensitive film without a coating manufactured in the abovemanner gives a more perfect saturation of the film mass than thehitherto know n impregnating process.

Moreover the improved process permits in a better manner than heretoforeto influence so important mechanical qualities of the film such ashardness, flexibility and the like further the infiammability of thefinishe product as well as to obtain the necessary esterility and'purityof the film mass'required for special photographic purposes.

It is a particular object of the present proc-3 ess to produce .acompletely transparent light sensitive cellulose film having no coatingwhich even inthe sensitized state is transparent like glass and whichpresents a considerable technical progress for thegsbecial purposes ,ofmaking reflex copies. (Player type). The hitherto known processes arelimited to soaked hygroscopic cellulose films in the manner of saltpapers or to impregnation by means ofbaths containing silver compoundsto cause the formation of silver chlorid or silver bromide within thebody' of, the-film whereby a certain sensitivity but not for thepurposes of the reflex copy.

The more or less pronounced dullness and cloudiness of the hithertoknown films made of hygroscopic cellulose by soaking them in solutionsof silver salts are due to the insuflicient penetration of thesensitizing solutions 1. A process for producing light-sensitiveinto theinterior of the film and by the precipitation ofsilver salts in zones inwhich ,unevenly swollen layers contact, further they are due toprecipitation effects between silver and chlorine of a smaller degree ofdispersion as well as to such exceeding the optimum of theconcentrationin silver. The manufacture of sensitized filmsv that areasclear as glass is made according to the present.

process in the following manner: After the film mass has been completelypenetrated by a suitable chlorine compound, for instance 4% sodiumchloride solution, the impregnation with the solution of silver salt forinstance with a 10%. solution of silver nitrate, is only then causeddirectly, if the chlorinated film mass is still as clear as glass afterdrying and if it does not opalize. The impregnation with silver saltsshall further only last as along as no formation of largeragglomerations occurs. If the film mass looks dull in any way after thechlorination a longer or shorter water bath has to be arrangedbefore theimpregnation with the solution of silver, this bath has also to be usedif a stronger solution of silver salt has to be applied.

I The manufacture of the sensitized films, which are as clear as glass,involves a great technical progress and is of the utmost importance formaking reflex copies. The use of these novel copying films presents alsoa great advantage in producing completely transparent and at the sametime true to scale copies and d'iapositive s, as such sensitive filmswhich have nocoating and are as transparent asglass permit a simpler andquicker treatment in the developing and fixing process and thereforetheyare less subject to the swelling influence of water.

I claim:

. negative andpositive films having no coating, which consists inincorporating sensitizing agents in the film mass of viscose during themanufacture of the film material.

2. A process for producing light-sensitive I negative and positive filmshaving no coat ing, which consists in 1ncorporating'sensitizing agentsin a film mass of viscose immediately after the coagulation of the filmmaterial and before final drying.

3. A process for producing light-sensitive negative and positive filmshaving no coating, which consists in incorporating sensitizing-agents ina film mass of viscose immediately after the coagulation and the washingof the film material andbefore completion of the film by drying.

4. A process for producing light-sensitive negative and positive filmshaving no coating, which consists in incorporating at least onecomponent of the sensitizer in a film mass of' viscose during themanufacture of the 21m material and before final drying of the 5. Aprocess for producing light-sensitive negative and positive films havingno coating, which consists in incorporating a silver salt in a film massof viscose during the manufacture of the film material.

6. A-process for producing light-sensitive negative andpositive filmshaving no coating, which consists in incorporating atleast one componentof the sensitizer in a film mass of viscose during the manufacture ofthe film material, the concentration of the sensitizer and the manner ofincorporation being so chosen that the film mass remains perfectlytransparent. v

' 7 A process for producing light-sensitive negative and diapositivecellulosic films from viscose, having no coating, and having thesensitizer incorporated withinthe body of the film, which consists inincorporating sensitizing agents in the film mass during the manufactureof the film while the "latter is .still in its swelled condition andbefore it is ultimately dried.

8. A process for producing light-sensitive negative and diapositivecellulosic films from viscose, having no coating, which consists inincorporating at least one component of the sensitizer in the film massduring the manufacture of the film while the latter is still in itsswelled condition before it is ultimately. dried.

9. A'. process for producing light-sensitive negative and diapositivecellulosic films from viscose, having no coating, which consists inincorporating at least one component of the sensitizer in thefilm massduring the manu-i facture of the film, the concentration of thesensitizer and the manner of incorporation being so chosen that the filmmass remainsperfectly transparent.

' 10. A process for producing light-sensitive negative and diapositivecellulosic films from viscose, havingno coating, and having thevsensitizer incorporated within the body of the film, substantially asdescribed.

11; A process for producing viscose photographic films having nocoating, which comprises introducing into the film during itsmanufacture and while in a swollen condition, a sensitizing agent, thefilm being hardened by a hardening agent.

12, A glass-clear grain-freeviscose photographic film, sensitized in itsbody and substantially free from subsequent alteration upon developmentand spots due to opalescence and uneven charging of sensitizer resultingfrom uneven swelling of the film.

In testimony whereof, I have signed my name to this specification. I

ULRICH DIEM-BERNET.

